Corrugated cardboard manufacturing process

ABSTRACT

The invention relates to a process for manufacturing corrugated board in which the corrugated board is produced by gluing at least three individual constituent webs (3, 5, 7) respectively on two sides oriented toward each other, wherein in a single work cycle, at a first glue application point (A), a first constituent web (3) is coated with glue and at a second assembly point (B), the first constituent web (3) is glued to a second constituent web (5) to form a half-finished web (31), and wherein in the same work cycle, at a second glue application point (D), glue is applied to a third constituent web (7) or to the half-finished web (31) and the third constituent web (7) is glued to the half-finished web (31) at a second assembly point (C) that is removed in the web travel direction in relation to the first assembly point (B). Furthermore, the invention relates to a device for carrying out the process according to the invention.

BACKGROUND OF THE INVENTION

The invention relates to a process and a device for manufacturingcorrugated board, in particular, quintuple or double-double corrugatedboard.

For the assembly and gluing of at least three individual constituentwebs, as is required, for example, in the manufacture of quintuple, i.e.so-called double-double corrugated board, up to this point, as a rule, atriple preheater has been used as an independent unit as well as asubsequently disposed double glue application mechanism, likewise usedas an independent unit. With the aid of the glue application mechanism,two out of three webs to be glued are coated with glue on one surfaceand are supplied to a press device, together with another web that hasnot had glue applied to it. In other words: after glue is applied to twoout of three webs to be glued together, they are assembled with thethird web at a single point and the mutually opposing surfaces of theindividual constituent webs are pressed against one another. As a rule,the assembly of the constituent webs takes place in a gluing machinewith two inlet rolls oriented perpendicular to the web travel, by meansof which the individual constituent webs are supplied to a heatingsection that serves to harden the glue and dry the finished web. Inorder to achieve a rapid gelling of the glue and thereby a rapid wetgluing after the assembly of the webs, it is necessary to heat at leastthe webs to be glued before the application of the glue. To this end, apreheater with a number of preheating cylinders is usually disposedbefore the double glue application mechanism.

With this known process and this known device for producing multilayercorrugated board, in particular, quintuple or double-double corrugatedboard, however, it is disadvantageous that relatively large web lengthsare required between the glue application points of the double glueapplication mechanism and the assembly point of the individualconstituent webs in the gluing machine. Depending on the temperature ofthe webs supplied to the gluing mechanism, this brings about the dangerthat too much moisture is extracted from the glue before the start ofthe gelling process, which has a disadvantageous effect on the adhesionstrength of the glue when the individual constituent webs are broughttogether. Also, due to the size of the gluing mechanism, it is onlypossible--if at all--to shorten the web length of all of the constituentwebs between the glue application point and the assembly point to thedesired size when there is a large structural expenditure. Furthermore,the relatively large distances between the preheaters and the webassembly point results in an intense cooling of the individual webs,which at the same time leads to the fact that the web does not have theoptimal temperature sought for the gluing.

SUMMARY OF THE INVENTION

The object of the invention, therefore, is to create a process and adevice for producing corrugated board, wherein the above-mentioneddisadvantages are prevented and a corresponding adhesion force of theglue is rapidly achieved after the assembly of the individualconstituent webs.

Through the assembly of only two respective constituent webs in anassembly point and the concomitant positional separation of the twogluing mechanisms, it is possible to keep the web length between theglue application points and the assembly points small so that because ofthe correspondingly low web travel time, particularly at low speeds, animpermissibly large quantity of moisture is not withdrawn from the gluedue to the penetration of moisture into the glued web.

The maximal web length between the glue application point and theassembly point is preferably chosen so that the web travel time isapproximately 200 ms at maximal speed, which corresponds to a web lengthof approximately 1 m at a web speed of 300 m/min.

Since the webs are preheated before the glue application, there is thefurther advantage that in comparison to known processes and devices, thewebs cool off significantly less leading up to the assembly point sothat this heat is still available for the gelling and hardening of theglue as well as for the drying of the glued webs. The length of thesubsequent heating section can be reduced as a result of this.

In the preferred embodiment of the process according to the invention,the half-finished web, i.e. the two constituent webs that have beenglued together first, are heated between the first and second assemblypoint at least on the surface that is glued to the surface of the thirdconstituent web oriented toward it at the second assembly point. Thisboth accelerates the gelling process or the hardening of the glue andshortens the drying time for the finished corrugated board web. Thissupply of a sufficient quantity of heat to later intermediary layers ofthe finished web can likewise significantly shorten the length of thesubsequent heating section in comparison to known devices.

In the preferred embodiment of the device according to the invention,the preheater, the press device, and/or the gluing mechanism areembodied so that they can be combined or integrated into one unit. Thisachieves the desired shortening of the web lengths between the preheaterand the glue application point or between the preheater and the assemblypoint in a simple manner.

Embodying the preheater, the press device, and/or the gluing mechanismso that they can be assembled or integrated into one unit is naturallynot limited to the case in which at least three constituent webs areglued together to form a corrugated board, but can also be used whenonly two individual constituent webs are to be glued to each other, asis the case, for example, in the manufacture of a double-sidedcorrugated board comprised of a one-sided corrugated board and a simpleweb.

In the preferred embodiment of the device according to the invention, aheating device is provided between the two assembly points and suppliesa predetermined quantity of heat to both surfaces of the half-finishedweb. The unheated web length between this heating device and the secondassembly point is likewise preferably kept as short as possible in orderto prevent an unnecessary heat loss.

In one embodiment of the invention, the heating device disposed betweenthe assembly points has a heated contact face for heating the onesurface of the relevant web and one or more heated press shoes extendingin the direction of and/or crosswise to the web movement direction,which press the web against the contact face and heat the other surfaceof the web. This preferably permits the elimination of an endless belt,which is disposed between the heated faces of the press shoes and is fortransporting the web, in order to prevent a heat transfer resistancebetween the heated surfaces and the web surface.

In another embodiment of the invention, the heating device can besubdivided into a number of segments in the web movement direction,wherein the segments preferably heat the one or the other web surface inalternating fashion. In this way, a transport device, for example in theform of a driven, endless conveyor belt, can be provided again in eachsegment, and at the same time, the heating of both surfaces of the webcan be assured. In contrast to the use of heated press shoes, though,the heating of the web surfaces does not happen simultaneously, butrespectively in succession, so that the length of the heating device hasto be chosen as correspondingly longer.

In an improvement of the device according to the invention, the heatedcontact faces of the segments can be embodied as alternatingly concaveand convex so that by means of the web being pulled through the segmentsdisposed one after the other, the web is pressed against the heatedcontact faces by means of the web tension alone. In this manner, the useof additional press elements can be eliminated. This heating device canalso be used not only in connection with the process or device accordingto the invention, but also in connection with every other device forproducing corrugated board or other devices for producing and treatingwebs.

In order to guarantee the necessary time for the withdrawal of moisturefrom the glue points when the web speed is increased, according to oneembodiment of the invention, the gluing mechanism can, if necessary, bemoved along with the mounted heating device so that the distance betweenthe assembly point of the constituent webs and the respectiveapplication point of the glue is increased.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in detail below in conjunction withexemplary embodiments represented in the drawings.

FIG. 1 shows a partially sectional schematic representation of anexemplary embodiment of the device according to the invention, forgluing at least three individual constituent webs;

FIG. 2 shows a partially sectional schematic representation of anotherexemplary embodiment of the heating device in FIG. 1 and

FIG. 3 shows a third embodiment of the heating device of the apparatusin FIG. 1;

FIG. 4 shows a schematic partial view of FIG. 1, with a movable unit forthe gluing mechanism and preheater.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The device represented in FIG. 1 is used for gluing together at leastthree individual constituent webs 3, 5, 7 and can as such be a componentof a corrugated board apparatus, not shown. The exemplary embodimentshown in FIG. 1 explains the process according to the invention or themanner of function of the device according to the invention in theexample of the manufacture of quintuple or so-called double-doublecorrugated board, which is comprised of three smooth webs and twocorrugated webs disposed between the smooth webs and glued to them.

Double-double corrugated board is usually manufactured by bringingtogether and gluing two one-sided corrugated board webs and one smoothweb. Correspondingly, the device 1 is supplied with a first one-sidedcorrugated board web 3, a smooth web 5, and a second one-sidedcorrugated board web 7. The one-sided corrugated board webs 3, 7 can besupplied in a standard way by one-sided corrugated board machines andthe smooth web 5 can be supplied from a conventional unwinding device ofthe corrugated board apparatus, not shown in detail.

The supply of the three constituent webs 3, 5, 7 is respectively carriedout by means of one or two deflection rolls 9. As is standard in theproduction of multi-layer corrugated board, the individual constituentwebs are first supplied to preheaters 11, 13, 15, and the webs areheated before the glue application and the respective assembly andgluing together.

As shown in FIG. 1, in comparison to conventional preheaters, thepreheaters 11, 13, 15 are embodied so that not just one but bothsurfaces of the web supplied to the preheater are heated.

To this end, each preheater 11, 13, 15 has a heated drum 17. This can beheated internally, for example by means of steam or in some othermanner. The drums 17 are supported in rotary fashion and can berespectively driven in the arrow direction indicated. The drum jacket iscomprised of very heat-conductive material, preferably metal.

The webs 3, 5, 7 supplied to the preheaters 11, 13, 15 rest with thesurface oriented toward the drum 17 against the drum jacket and windaround the drum with a predetermined winding angle. As they exit thedrum, the webs 3, 5, 7 are guided by means of a deflection roll 19 thatis preferably supported in rotary fashion. From the roll 19, the webs 3,5, 7 travel further via a heating face 21 against which they rest withthe surface that was not previously heated by the drum 17 as a result ofthe deflection by means of the relevant roll 19. In this manner, bothsurfaces of the webs 3, 5, 7 supplied to the preheaters 11, 13, 15 canbe heated.

Each heating face 21 is connected to the deflection roll 19 so that bothcan be pivoted concentrically to the axis of the drum 17. In thismanner, the device comprised of the heating face 21 and the deflectionroll 19 can be pivoted out of the position shown in FIG. 1, which hasthe maximal possible winding angle of the relevant web (3, 5, 7) aroundthe drum 17, until they are in a position in which the web winds aroundthe drum 17 with the minimal angle, wherein in this position, thesurface of the web 3, 5, 7 previously resting against the heating face21 is completely lifted away from the heating face. In the position withthe smallest winding angle, therefore, only the surface of the web 3, 5,7 resting against the jacket of the drum 17 is heated.

As shown in FIG. 1, the one-sided corrugated board web 3 is first heatedin the desired manner, for example on both sides, by means of thepreheater 11 and then is supplied to a first gluing mechanism 23. Thegluing mechanism 23 can be of a known type. After the application of theglue onto the ribs of the corrugated web of the one-sided corrugatedboard 3, this is supplied via another deflection roll 19, together withthe smooth web 5 to a press device 24 in the form of a pair ofcooperating rolls 25. The supply of the smooth web 5 is carried out inan analogous manner, i.e. the web 5 is also supplied with apredetermined quantity of heat on both surfaces by means of thepreheater 13. The rolls 25 now press the smooth web 5 against theglue-coated ribs of the one-sided corrugated board web 3 and thus carryout the gluing together of the two webs.

Through the relatively small web length of the web 3 between the exitfrom the heating face 21 of the preheater 11 and the glue applicationpoint A in the gluing mechanism 23, only a relatively slight coolingoccurs during the movement of the web between these points. Incomparison to known machines in which the relevant web length betweenthe exit from the heating face of the preheater and the glue applicationpoint is approximately 3 m or more, in the device according to FIG. 1achieves a significantly shorter web length through the directpositioning, mounting, or integration of the preheater onto or into thegluing mechanism. Concretely, web lengths of less than 1 m, preferablyless than 0.5 m can be achieved, which with a web speed of 300 m/min,corresponds to a web travel time of 200 ms or 100 ms. As a result of thelow web length between the preheater and the glue application point andthe slight cooling of the web connected with it, the gelling process ofthe glue after it is applied to the web acts more rapidly than in knownmachines so that after the assembly of the webs 3 and 5, a wet gluingoccurs very rapidly with a sufficiently high adhesion force.

At least as important as a low web length between the preheater and theglue application point is the achievement of as optimal as possible aweb length between the glue application point A and the gluing point orassembly point B, which is disposed between the two rolls 25 in theexemplary embodiment shown in FIG. 1. A short web length between theglue application point A and the assembly point B assures that duringthe travel time of the web between these two points, an impermissiblylarge quantity of moisture is not withdrawn from the glue due to thecapillary action of the web surface, which would have a disadvantageouseffect on the adhesion force.

Whereas in known devices for gluing at least three individualconstituent webs, two of the constituent webs are coated with glue andthen brought together with the third constituent web at a singleassembly point, with the device according to FIG. 1 or with the processrealized by means of this device, initially only the first constituentweb is glued to the second constituent web and only after this is thethird constituent web glued to the half-finished web thus produced.Through the use of two assembly points or gluing points B and C, only asingle gluing mechanism 23 or 27 must be disposed before each assemblypoint B, C, and precisely for this reason, this gluing mechanism 23 canbe brought very close to the assembly point B or C and makes anintegration of a preheater easier. This is not possible--or can only beachieved with a large structural expenditure--when two gluing mechanismsare used before a single assembly point, due to the size of the gluingmechanisms.

In comparison to known devices in which the distance between theunwinding point, the preheater, and the assembly point B is 5 m or more,with the process or the device according to the invention, as a resultof bringing the gluing mechanism, along with the preheaters, close tothe assembly point, which is now possible, a web length of 1.5 m or lesscan be achieved. At the same time, the web length between the glueapplication point A and the assembly point B is shortened byapproximately 2 m to approximately 0.5 m.

Preferably, the web length between the glue application point and theassembly point is less than 1 m, which at a web speed of 300 m/mincorresponds to a web travel time between the points A and B of less than200 ms. Between the glue application point A and the assembly point B,an additional heating device, not shown, can be provided for thecorrugated side.

After the assembly and gluing of the webs by means of the pair of rolls25, the half-finished web is supplied to a heating device 29, which--asshown in FIG. 1--preferably heats both surfaces of the half-finished web31 comprised of the webs 3 and 5 glued together.

To this end, the heating device 29 has a heated plate 33, which thehalf-finished web 31 rests against with its one surface (the bottom onein FIG. 1). The heating device 29 additionally includes one or moreheated press shoes 35, which preferably press the half-finished webagainst the heated undersides of the press shoes 35 and respectivelyagainst the surface of the heated plate 33 due to spring action by meansof springs 39 disposed in a frame 37. Naturally, both a number of pressshoes disposed one after the other in the web movement direction and anumber of press shoes lateral to the web can be provided. This achievesa uniform pressing of the half-finished web even when there is a slightunevenness of the web or of the heated surfaces.

The heating of both surfaces of the webs 3 and 5 supplied as well as thesmall web length between the preheater and assembly point B,simultaneously achieve the fact that it is possible to keep the lengthof the heating device 29 relatively short since this is not intended toproduce the complete hardening of the glue and drying of thehalf-finished web 31, but essentially serves to achieve a sufficientlyfirm (wet-) gluing inside the half-finished web before the supplying andgluing of the half-finished 31 to the third web 7.

Furthermore, the heating device 29 has the task of introducingadditional heat into the surface that adjoins the heated press shoes 35and is glued to the preheated one-sided corrugated board web 7. Thisheat introduced into the half-finished web serves to achieve a morerapid gluing of the web 7 to the web 31, which at a later point achievesa more rapid hardening and drying of the finished double-doublecorrugated board web.

The supply of the one-sided corrugated board web 7 is carried out in themanner described above for the supply of the one-sided corrugated boardweb 3. Bringing the preheater 15 as close as possible to the gluingmechanism 27 and disposing the gluing mechanism 27 as close as possibleto the assembly point C in turn achieves the advantages alreadydescribed above. The same is true for the double-sided heating of theone-sided corrugated board web 7 supplied.

Following the heating device 29, the half-finished web 31 passes throughanother heating device 41, e.g. in the form of heating shoes 41', whichonly heats the upper surface of the half-finished web 31, though, and inaddition has an endless conveyor belt 43 for the movement of thehalf-finished web 31 through the device according to the invention. Theendless conveyor belt 43 can also be heated. Furthermore, the endlessbelt 43 of the heating device 41, together with a press roll 45,constitutes a press device 46 for assembling and gluing thehalf-finished web 31 to the one-sided corrugated board web 7 at theassembly point or gluing point C.

FIG. 2 shows another embodiment of the heating device 29 according towhich the heating device is subdivided into individual segments in themovement direction of the half-finished web 31 and these segments serveto alternatingly heat the one or the other surface of the half-finishedweb 31. The individual segments are designed practically identically,but are alternatingly disposed in mirror image fashion on either side ofa horizontal axis. Each segment is comprised of a stationary heatedplate 47 with which one or several press shoes 49 cooperate. In contrastto the press shoes 35, though, the press shoes 49 are not heated andtherefore can exert their pressure onto the half-finished web 31 bymeans of a revolving, endless belt 51, wherein the endless belt 51carries out the transport of the half-finished web 31 through the deviceaccording to the invention.

The heating device 41 could also be embodied in the same way.

In another embodiment of the heating device 29 according to FIG. 3, theheating plates 47 can be embodied as alternatingly concave and convex sothat no press shoes are necessary for pressing the half-finished web 31against the heated surface of the plates 47 since the pressing isalready achieved by means of the tension in the half-finished web 31.

As shown in FIG. 4, the gluing mechanism 23 and the preheater 11 arecombined into one unit 40. The unit 40 is movably supported on thepreheater 13 so that it can move by means of rolls 41 on projectingrails 42.

If the web speed V is increased, the unit 40 can be moved toward theleft in the drawing of FIG. 4. This increases the distance between theglue application point A and the constituent web assembly point Bconstituted by the press device 24. In this manner, the sufficientmoisture withdrawal of the glue application is assured despite theincreased web speed. The moisture withdrawal of the glue application iscarried out by means of the capillary action of the constituent web.

In the same manner, the unit, not shown, which adjoins the heatingdevice 29 and contains the preheater 15 and the gluing mechanism 27, canbe embodied so that it can move.

The moving of the unit 40 can be carried out manually or automaticallyas a function of the web speed V. A conventional drier section can comeafter it.

What is claimed is:
 1. A process for manufacturing corrugated board, bygluing together at least three individual constituent webs together onfacing surfaces of the webs, comprising the steps of:a) in a work cycle,at a first point, a glue application point, coating a first web withglue; b) at a second point, an assembly point, gluing the first web to asecond web to form a half-finished web by passing the first web and thesecond web through a press device; c) in said work cycle, at a thirdpoint, a glue application point, coating a facing surface of a third webwith glue; d) downstream of the second point, an assembly point, heatingopposite faces of the half-finished web by passing the web through aheating device comprising a heated press shoe opposite a first face ofthe half-finished web and a heated plate opposite a second face of thehalf-finished web opposite to the first face, without application ofglue thereto; and (e) at a fourth point, an assembly point that isdownstream in relation to the second, assembly point, gluing togetherfacing surfaces of the third web and the heated, half-finished web bypassing the third web and the heated, half-finished web through a pressdevice, to form the corrugated board.
 2. The process according to claim1, wherein the web travels between the first point, a glue applicationpoint, and the second point, an assembly point, in a time less than orequal to 200 ms.
 3. The process according to claim 1, wherein at leastone of said first and third webs is preheated before being coated withglue.
 4. The process according to claim 1, wherein the second web is notcoated with glue and is also heated before being glued with the firstweb.
 5. The process according to claim 3, wherein the at least one webwhich is preheated travels between the end of preheating and asubsequent glue application point in a time less than or equal to 200ms.
 6. The process according to claim 1, wherein the corrugated board isheated on at least one surface after gluing together said third web andsaid half-finished web.
 7. The process according to claim 1, wherein thefirst point, a glue application point and second point, an assemblypoint are separated by a distance which is changed as a function of webspeed.
 8. The process according to claim 1, wherein the third point, aglue application point and fourth point, an assembly point are separatedby a distance which is changed as a function of web speed.
 9. Theprocess according to claim 1, wherein the corrugated board is heated onat least one surface after assembly of all webs.
 10. The processaccording to claim 1, wherein the web travels between the third point, aglue application point, and the fourth point, an assembly point, in atime less than or equal to 200 ms.
 11. A device for manufacturingcorrugated board by gluing together at least three individual webs ontwo facing surfaces comprising:a) a first gluing mechanism for applyingglue to a first web; b) a first press device disposed downstream of thefirst gluing mechanism for assembling and gluing together the first websupplied thereto coated with glue and a second web supplied thereto toform a half-finished web; c) a second gluing mechanism for applying glueto a facing surface of a third web; (d) a second press device forassembling and gluing together an unglued facing surface of thehalf-finished web and the glued facing surface of the third web; and (e)a heating device provided between the first and second press devicesconstructed and arranged for heating both surfaces of the half-finishedweb, said heating device comprising a heated press shoe and a heatedplate constructed and arranged such that the half-finished web passestherebetween.
 12. The device according to claim 11, additionallycomprising at least one preheater constructed and arranged for heatingat least one surface of the first web disposed upstream of either thefirst gluing mechanism or upstream of the first press device.
 13. Thedevice according to claim 11, additionally comprising at least onepreheater constructed and arranged for heating at least one surface ofthe third web disposed upstream of either the second gluing mechanism orupstream of the second press device.
 14. The device according to claim12, wherein web length between the first preheater the first pressdevice is minimized.
 15. The device according to claim 14, wherein thepreheater, the first press device, and/or the first gluing mechanism areconstructed and arranged to be integrated or combined into a singleunit.
 16. The device according to claim 11, wherein the heating devicecomprises a heated contact face for heating one surface of thehalf-finished web and at least one heated press shoe extending laterallywith respect to web movement and which presses one face of thehalf-finished web against the contact face and heats an opposite face ofthe half-finished web.
 17. The device according to claim 11, wherein thegluing mechanisms are movable so that its distance to its respectivepress device can be increased as web speed increases and decreased asweb speed decreases.
 18. The device according to claim 17, wherein thedistance increase or decrease is carried out manually or automaticallyby moving the gluing mechanism.